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AQUEDUCTS OF ROME UNDER AUGUSTUS
Part One

The Augustan era was perhaps the greatest period
of construction in ancient Rome. One of the more important aspects of this program
was the repair and renewal of the city's system of aqueducts. At that time,
the city was served by four aqueducts-the Appia, Anio Vetus, Marcia and Tepula.
All of these were in great need of repair and augmentation, since the most recent
was almost a century old.[1] Up to Augustus'
time, Rome had little time or resources for anything but minor work on
the water supply. She
had gone through the civil strifes of Marius and Sulla, a major slave revolt
and two civil wars. Rome had grown to a population of close to one million
and
was in dire need of a better water supply. Augustus could see a distinct
political advantage to the restoration and revamping of the water system.
This would more
firmly establish his regime and present a positive benefit to the populace.

In this article, the first
of two parts, I will go into the establishment of the centralized water office
and the restoration of
the older aqueducts. In the second part, I will treat the construction of the
new aqueducts--the Julia, Virgo and Alsietina. As an aid to the understanding
of all these aqueducts, I refer you to the two illustrations below, showing
the various aqueducts. They show all the aqueducts, including those post-date
the reign of Augustus, one showing them on
a map of modern Rome and one on ancient Rome.

click on images for enlargements

As with many difficult
matters, Augustus chose M. Vipsanius Agrippa to carry out the new water
program. At this time, Agrippa
was both his son-in-law and his most able general. He had been praetor in 40,
consul in 37 and was instrumental in the defeat of Sex. Pompeius in 36.
Augustus
set him to work repairing the Aqua Marcia in 34. In 33, Agrippa consented to
go the reverse of the cursus honorum and take the lower rank office
of aedile, in order to work full time on the project.[2] In
this year, Agrippa extensively restored the Appia, Anio Vetus, Marcia,
and combined
the Tepula with a new aqueduct, the Julia. In order to accomplish such an extensive
program, a central administration needed to be set up. According to Dio
Cassius,
he did this with his own funds[3] and staffed it with his
own
familia of slaves, at least for the maintenance of the system. According
to Frontinus, this numbered 240 individuals, who were left to the state upon
his death. The emperor Claudius added a later group of 460 from the familia
publica to this at a later date. These numbers remained the same even
up until the time of Frontinus, who was curator aquarum under Trajan[4]
when he wrote his book on the subject. Agrippa is also credited with inventing
the standard of measurement for the office, the quinaria. This, however,
is not a measure of volume, but of capacity. It measured how much water could
be discharged through a pipe 5/4 of a digit in diameter, flowing under constant
pressure. This measures out to about 5,000 to 6,000 gallons per 24 hours. [5]

Agrippa continued unofficially as curator aquarum
until his death in 12. In 11, Augustus named a new curator, M. Valerius Messalla
Corvinus, who had previously served as praefectus urbis. He served until
his death in 13 AD. He was succeeded by C. Atius Capito, who continued in office
into the time of Tiberius. The Senate passed a series of consulta defining
the powers and privileges of the office, also in 11.[6]

I will start with the restoration of the Appia. This
was the oldest of the Roman aqueducts and by far the crudest.[7]
Agrippa began his repairs on it in 33. Unfortunately, it cannot be determined
to what extent, due to the lack of knowledge of its exact route outside of the
city. However, one would expect it to have been extensive. Augustus in his later
renovations from 11 to 4, augmented the Appia with a branch which joined it
just outside Rome near the temple of Spes Vetus. This branch came to be known
as the Ramus Augusta or just the Augusta Appia. This appears to have been in
the vicinity of the Porta Maggiore.[8] There is a small section
which might be it, just about a block inside of and a block to the left of the
Porta Maggiore. It displays typical Augustan opus reticulatum lining and what
appears to be either a thin covering of plaster or lime deposits from the water.
I took some photos of it in 1973 and they can be seen below.

It should be born in mind,
though, that the Appia was the earliest aquaduct. At that time the Roman
engineering was not at its
peak. It and many of the earliest aqueducts were not borne aloft on the stately
arches that we are accustomed to when we think of Roman aqueducts. They were
constructed by a cut and cover method. This is where a trench would be dug,
the channel lined with stone, or concrete, closed on top with corbeled or
flat
slabs and then covered over with earth. This had its advantages in that it
was a simpler and less costly structure and also less likely to be attacked
by enemies.
Bear in mind that at the time of its construction, Italy and the environs of
Rome were not unified. Rome still had enemies and a good source of water
would
be a tempting target. Buried, it was much less obvious. As can be seen in the
second photo of this section, the aqueduct was still at ground level or just
a little higher. The need for concealment was not needed, but the elevation
was necessary for the continuation of the flow. Here it can be seen that
the
channel was now of arched concrete. The exterior shows some of the aggregate
sticking out of the mass. Whether it was encased further for aesthetics,
I do
not know. Looking at the interior shots, you
can see the fine opus reticulatum work mentioned above. Similar work can be
seen in further photos on the Anio Vetus in this article.

Agrippa also restored the Anio Vetus in his aedileship
and later by Augustus, who marked it with its only cippi. The intake of this
aqueduct was discovered by Ashby in 1915, but has since been reburied. He found
it to be of Augustan concrete. Further example of Augustan concrete has also
been found on the section at Ponte degli Arci. At the Ponte Lupo, there remains
a very deeply sunken shaft, which seems to be part of an inverted siphon. This
shaft is supported by a thick buttress of large dimensions. The buttress and
the shaft are both of Augustan concrete, faced both with tufa reticulate and
small rectangular blocks. This all points to a reconstruction in the period
of 11-4 by Augustus. The lack of any traces of a bridge or by-pass and the great
depth of the shaft strongly point to the Anio Vetus passing beneath the stream
in an inverted siphon and I illustrate this in the next two illustrations.

The
inverted siphon is a bold and costly device. It is used to carry the water
across a
valley or ravine, but without the
massive substructures to bridge the valley at the same level as the surrounding
valley sides. It works on the principle of water seeking its own level.
As long as the "downstream" side is at or lower than the "upstream
side" , the water pressure and capillary attraction will maintain
the flow. However, as Vitruvius notes,[9] there is need
for standpipes to reduce the air pressure in the pipes and multiple pipes
rather than just the one, also to reduce the pressure.

Roman
architects usually avoided using this device due to the cause and potential pressure
problems. They much preferred to detour around the obstacle in laying the channel.
It is odd that they used it here, as the high lime content of the Anio would be
expected to choke the small pipes used. Concrete pipes of a larger size would
not be used, as the Romans did not regard concrete as suitable for this purpose.[10]

One other notable example of the Anio Vetus is to
be found just outside the Porta Maggiore on the eastern side of the Via Labicana.
Some of the sections in this area have been found showing both the original
channel and the Augustan restorations. One of these sections, shown below, runs
for 140 meters and is another fine example of Augustan opus reticulatum. The
channel is constructed of gray, friable Augustan concrete. It is faced both
on the channel proper and the substructures with a tufa reticulate. Similar
work is to be found on the Anio Vetus inside the city in underground channels
neat the intersection of the Via Principale Umberto and the Piazza Fanti as
well as a reservoir. It also compares well with the work seen above on the Appia.

Since the next aqueduct,
the Marcia, is often found in conjunction with the later Tepula and the Augustan
Julia, I will treat that
in the next part.

Al Schlaf earned a degree in Classical Languages and History at The Florida State University, with post graduate work at Florida State, University of Iowa and Trinity College of Hartford, Conn./Rome, Italy Campus.

He currently teaches in the Des Moines Public School system in Des Moines, IA.